17 
IO- 8-63 cont. 
with much vocalization and the bills of the contestants usually 
end up locked: Then there is tugging, pulling, and lots of 
noise. Then very quickly it is over with the contestants looking 
rather bewildered. The fight resumes when the head shaking on 
both sides begins again. The same head shaking movements are 
used when the young beg food from the adults. However, 
a different call accompanies this display, and the adults' are 
usually silent. I have the distinct impression that some of 
the adults “‘know’' that they are being 11 taken ” from the 
expressions on their faces after disgorging food. The young’s 
food call is a series of rapid yuk-yuk-yuk-yuk notes given 
in rythm to the head movements. Young birds spent a lot of 
time begging food, and after an adult has been with the hungry 
waif for several hours and has no more food to give the chick, 
I believe that they may leave the territory and rest elsewhere 
to get a-gay from the chick which as often as not follows the 
adult. 
10 - 9-63 
Began making temperature observations on the different 
microenvironments here and the birds that occupy them ( See 
Appendix 4 j. 'worked at this most of the day and helped Bill 
set his traps again. Obtained 37 bird temperatures, and 
fifteen microenvironment temperatures. It seems as if the 
island is a heat resovoir at night, and lacks heat early in the 
day. The island seems to reach equilibrium each day at 0930 and - 
2045, when all environments have about the same temperature, 
about 27.3 degrees C at 0930* and about 25»1 degrees centigrade 
at 2045. This daily temperature cycle is,of course, a direct 
result of the daily weather pattern. However, the relatively d. 
warm lagoon temperature and constant winds seem to keep the islan 
in a very homogeneous temperature state. Except when there is 
rain, the daily Temperature cycle probably is no more than 
7-10 degrees centigrade for most of the island where there 
is vegitation. Bare soil fluctuates more than that. 
Notes on Sub-Adult Masked Booby Plumages: 
I have now seen three Subadult Masked Boobys ( all banded, 
one specimen No. 667-70640 ) shoving vestiges of immature plumage, 
In this plumage the coverts of the secondaries, tertials, 
upper tail coverts, and occasionally a few of the lower 
( posterior ) back feathers show the mottling of black whi ch 
ischaracteristic of most of the feathers in Juvenals. This reteii- 
pion of the immature plumage apoarently varies considerably 
with individuals. The iris of the eye is dusky yellow at this 
plumage also. It is perhaps significant that I have captured only 
females in this plumage thus far: It again suggests that 4 birds 
are more skittish, and are less attached oo the Breeding gioundso 
99K 
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